Preliminary experiments have produced an animal model for the DES problem in young women. In common with the human condition the mouse model has a high incidence of vaginal adenosis and associated anomalies produced by transplacental exposure to DES (diethylstilbestrol). One objective of the grant proposal is to describe this model more completely, including frequency of adenosis and the other anomalies at various periods in the life cycle of female offspring. The rates of spontaneous tumor formation will be compared in control and DES-exposed mice throughout their lifespans. Another major objective is to test the effect of contraceptive steroids on the tumor incidence of adult female mice exposed prenatally to DES as compared to vehicle-injected controls. A study of maternal susceptibility to cancer after DES treatment will be initiated.